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A Case Study of Vibroseis High-efficiency Flip-flop Sweep Technique

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Ruyi, Zhou, Mugang, Zhang, Shuquan, Deng, and Hong Yueying. "A Case Study of Vibroseis High-efficiency Flip-flop Sweep Technique." Paper presented at the 2006 SEG Annual Meeting, New Orleans, Louisiana, October 2006.

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With the continuous development of vibrator electronics, the flip-flop sweep technique for vibroseis has been widely used in industry. Based on the conventional sweep technique, this paper developed a high-efficiency flip-flop sweep technique for vibroseis. The production efficiency for this application is 30% higher than conventional flipflop sweep operation and 67% higher than the operation method with only one fleet of vibrators. This technique has wide applicability.

The application of vibroseis has played an important role in seismic exploration. Compared with explosive seismic sources, vibroseis methods have unique advantages: the source signal is known and the frequency-band and the energy of signal are controllable. The new generation vibrator electronics such as VE432 vibrator electronics, provides real-time QC. The vibroseis’s controller integrates a set of automatic detection functions by measuring the coherence to ensure the vibroseis’s excitation quality and to generate the corresponding signal without the risk of polarity error. The QC analysis of phase, distortion and the output force etc. can be generated by vibrator’s controller. In addition, the datasets also can be used for recognizing the near-surface structure parameters, for example, the elasticity and damp, which explain the earth’s absorption so as to guide seismic data processing. The high-efficiency flip-flop sweep technique is promoted by development of vibrator electronics and it will play more and more important roles in seismic exploration.

The flip-flop sweep uses two vibrator fleets with which function switching during the operation procedure, namely, when one group of vibrators is working, the other group of vibrators can move to next shot point. With this operating mode, the time between two successive sweeps can be much shorter, improving production efficiency. Suppose two vibrator fleets are deployed and four vibrators are involved for each sweep. The sweep length is 12s with two sweeps for each VP by moving up 25m shooting. The record’s length is 5s. Theoretically, for a single fleet operating mode of vibroseis when the first sweep finishes, the group moves 25m and shakes the second sweep, then moves the vibrators and takes a record. After that, the same operating mode is used to finish the second shooting. In this way, one shot’s period is 74s. In the case of double vibrator fleets, suppose we use the conventional flip-flop sweep ,namely, when two sweeps for one shot are finished, the second vibrator fleet works immediately, meanwhile, the first vibrator fleet moves to the next shot point. In this way, there will be no waiting time between two shootings, so that shooting period is shorter. The period for each shot is 59s and the production efficiency is 25% higher than the single vibrator fleet. In order to further improve the production efficiency, we present a higher-efficiency flip-flop sweep technique than the conventional mode. The core of this technique is to alternately record each sweep of the two vibrator fleet: when one vibrator fleet moves, the other one shoots one sweep and takes a record and starts to move..

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Flip-Flop Quizzes: A Case Study Analysis to Inform the Design of Augmented Cognition Applications

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• Branden Ogata 10 ,
• Jan Stelovsky 10 &
• Michael-Brian C. Ogawa 10  

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This paper examines the effectiveness of Flip-Flop quizzes, a pedagogical methodology in which students create quizzes synchronized with lecture videos as part of an inverted classroom. In order to generate quality quizzes, students must understand the material covered in the lecture videos. The results of our study inform the design of augmented cognition applications.

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Ogata, B., Stelovsky, J., Ogawa, MB.C. (2020). Flip-Flop Quizzes: A Case Study Analysis to Inform the Design of Augmented Cognition Applications. In: Schmorrow, D., Fidopiastis, C. (eds) Augmented Cognition. Human Cognition and Behavior. HCII 2020. Lecture Notes in Computer Science(), vol 12197. Springer, Cham. https://doi.org/10.1007/978-3-030-50439-7_7

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Few Drugs Display Flip-Flop Pharmacokinetics and These Are Primarily Associated with Classes 3 and 4 of the BDDCS

Kimberly l. garrison.

1 Department of Bioengineering & Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA;

2 Present Address: Gilead Sciences, Inc., Foster City, CA, USA

Selma Sahin

3 Hacettepe University, Faculty of Pharmacy, Ankara, Turkey

Leslie Z. Benet

To determine the number of drugs exhibiting flip-flop pharmacokinetics following oral dosing from immediate release dosage forms and if they exhibit a common characteristic that may be predicted based on BDDCS classification.

The literature was searched for drugs displaying flip-flop kinetics (i.e. absorption half-life larger than elimination half-life) in mammals in PubMed, via internet search engines and reviewing drug pharmacokinetic data.

Twenty two drugs were identified as displaying flip-flop kinetics in humans (13 drugs), rat (9 drugs), monkey (3 drugs), horse (2 drugs), and/or rabbit (2 drugs). Nineteen of the 22 drugs exhibiting flip-flop kinetics were BDDCS Classes 3 and 4. One of the three exceptions, meclofenamic acid (Class 2), was identified in the horse however it would not exhibit flip-flop kinetics in humans where the oral dosing terminal half-life is 1.4 hr. The second, carvedilol, can be explained based on solubility issues, but the third sapropterin dihydrochloride (nominally Class 1) requires further consideration.

The few drugs displaying oral flip-flop kinetics in humans are predominantly BDDCS Classes 3 and 4. New molecular entities predicted to be BDDCS Classes 3 and 4 could be liable to exhibit flip-flop kinetics when the elimination half life is short and should be suspected to be substrates for intestinal transporters.

Introduction

Accurate prediction of in vivo pharmacokinetics from in vitro measurements is an ongoing goal in the field of pharmaceutical sciences and was a primary incentive in the establishment by Amidon and colleagues 1 of the Biopharmaceutics Classification System (BCS). Wu and Benet 2 built upon the BCS by modifying it to include information concerning drug elimination, and thus created the Biopharmaceutics Drug Disposition Classification System (BDDCS; Figure 1 ) to aid in predicting in vivo drug disposition by identifying the role of drug transporters, here presented with respect to effects in the intestine, as reviewed by Shugarts and Benet 3 . The BDDCS gives scientists and clinicians a tool for predicting drug disposition and drug-drug interaction characteristics very early in development and with little additional expense. This paper is dedicated to Professor Amidon in recognition of his outstanding and seminal contributions to the pharmaceutical sciences. It would not have been possible to conceive of the BDDCS 2 , without his prefatory insightful development of BCS 1 .

Gastrointestinal absorption is generally faster than elimination for most immediate-release, orally dosed drugs. However, there are exceptions characterized as flip-flop pharmacokinetics, in which the rate of absorption of a drug is slower than its rate of elimination. It is termed “flip-flop” because the absorption is the limiting process for elimination, since a drug cannot be cleared from the system any faster than it enters into that system. It follows that observing an increased terminal elimination half-life following oral (p.o.) dosing of a drug, as compared to its intravenous (i.v.) half-life, is indicative of flip-flop pharmacokinetics. That is, while the ratio of a drug's absorption half-life to its elimination half-life (t 1/2,abs /t 1/2,elim ) is usually less than one, in the case of flip-flop kinetics the ratio is greater than one. In 2011, Yáñez et al. 4 published an extensive review of flip-flop pharmacokinetics, identifying 12 drugs exhibiting flip-flop pharmacokinetics following immediate release oral dosing.

It is hypothesized here that drugs exhibiting poor intestinal membrane permeability rate would be those most likely to display flip-flop kinetics, as also noted by Yáñez et al. 4 Poorly permeable drugs generally have a low oil-to-water partition coefficient and are classified as BDDCS Classes 3 and 4, which are poorly metabolized. This report describes nineteen drugs that display flip-flop kinetics and are poorly metabolized, although one of these poorly metabolized drugs displays a very weak flip-flop profile. These drugs are all associated with Classes 3 and 4 of the BDDCS. Based on these classifications, the BDDCS predicts that absorptive (uptake) transporters may play an important role in the gastrointestinal absorption of Class 3 and 4 drugs ( Figure 1 ). Here we suggest that in vitro measures of permeability rate and extent of metabolism will predict whether or not a drug would be likely to display flip-flop kinetics in vivo .

Drugs described in the literature as displaying flip-flop kinetics after oral dosing of immediate-release formulations in mammals (humans, monkeys, horses, rats or rabbits) were identified in a survey of previously reported pharmacokinetic studies. Searches using the term “flip-flop [or flip flop] kinetics [and pharmacokinetics]” were performed in both PubMed, Web of Science, via various internet searches (e.g. Google) and reexaminations of specific drug categories as will be described. The search results were then gleaned to identify reports of flip-flop drugs and their respective i.v. and p.o. half-lives. Studies investigating controlled release formulations, prodrugs or drugs administered via non-oral delivery sites (e.g. intramuscular, inhalation, etc.) were excluded from consideration. Close to 200 studies identifying flip-flop pharmacokinetics were found via the search processes utilized, with the overwhelming majority related to formulations developed to achieve flip-flop pharmacokinetics for drugs with short half-lives. For example, a recent publication reports flip-flop kinetics for the Class 1 drug mycophenolate in transplant patients for an enteric-coated formulation 5 . Similarly, drugs with non-enzymatically catalyzed metabolism (e.g. thalidomide 6 ) or drugs reported to display flip-flop kinetics under conditions of decreased intestinal motility that would affect absorption kinetics were also excluded (e.g. cephradine 7 or dabigatran etexilate 8 , 9 ). Two additional drugs were excluded due to a lack of corroborating evidence in the literature: a report of possible flip-flop kinetics of etoposide in children was ambiguous 10 ; a single report of the i.v. half-life of vildagliptin in humans 11 was within the range of p.o. half-lives reported in other human studies 12 , 13 , and in addition, studies with vildagliptin in rats clearly demonstrated a lack of a flip-flop phenomenon 14 .

Where available, the reported terminal half-life after p.o. dosing of a drug was compared to the elimination half-life after i.v. dosing, and a ratio was calculated for each. Drugs were then classified into the BDDCS based on solubility and extent of metabolism following the tabulation of Benet et al. 15 . A drug is said to be highly soluble in both BCS and BDDCS when its highest dose strength is soluble in 250 mL or less of aqueous media over the pH range of 1-7.5 at 37°C 2 . Drugs were classified as highly metabolized if metabolism accounts for at least 60% of its elimination 15 . Of the 22 drugs found to exhibit flip-flop kinetics, 13 had a published BDDCS classification 15 . The remaining nine were classified based on the above criteria. Further searches of the literature were done to identify which of these drugs were known substrates of the uptake and efflux transporters expressed on the intestinal lumen and liver.

Acamprosate, amoxicillin, ampicillin, calcium dosbesilate, carbovir, carvedilol, cefuroxime, cephalexin, fexofenadine, florfenicol, furosemide, levovirin, meclofenamic acid, metformin, nitrofurantoin, pravastatin, rebamipide, sapropterin, xamoterol, zanamivir and zidovudine are reported to display flip-flop kinetics, and nedocromil is reported to show a weak trend toward flip-flop kinetics ( Table 1 ). Each of these drugs, except for carvedilol, meclofenamic acid and sapropterin, is eliminated primarily through excretion (i.e. poorly metabolized) and thus is assigned to Classes 3 or 4 of the BDDCS. Interestingly, zidovudine displays flip-flop kinetics in rats 16 , where it is poorly metabolized (20-30 % metabolized 17 - 19 , as compared to both monkeys 19 , 20 and humans 19 , 21 , 22 in which zidovudine displays normal kinetics and is extensively metabolized (60-75 % metabolized).

In the majority of cases presented in Table 1 , the slow absorption process after an oral dose had a very obvious impact on pharmacokinetics and resulted in an observed terminal half-life that was longer by about two-fold or greater as compared to the i.v. dose elimination half-life. One clear exception was nedocromil, for which the flip-flop trend was weak and the absorption half-life to elimination half-life ratio was closer to one ( Table 1 ). Notably, nedocromil has an inherently longer elimination half-life (13.8 h) than any of the other drugs (0.3 – 7.7 h) that displayed convincing flip-flop kinetics. Two BDDCS Class 2 drugs 23 - 25 and one Class 1 drug 26 are reported to exhibit flip-flop pharmacokinetics.

Classification into the BDDCS helps to predict whether uptake and/or efflux transporters in the gut will play a role in the absorption of a drug 2 , 3 ( Figure 1 ). The effects of transporters on the absorption of Class 1 compounds are negligible. For Class 2 compounds, the effects of efflux transporters are expected to dominate in the gut. The BDDCS predicts that absorptive transporter effects will predominate for Class 3 drugs, although efflux transporters in the gut may potentially modulate their disposition. For Class 4 drugs, the BDDCS predicts that the drug's disposition is likely to be to be affected by both absorptive and efflux transporters. Eighteen of the 21 drugs (omitting zidovudine) with flip-flop kinetics identified herein were poorly metabolized and thus classified as either Class 3 or 4. We recently reviewed intestinal drug transporters 27 and only half of the drugs exhibiting flip-flop kinetics have been previously shown to be substrates for at least one uptake and/or efflux transporter (not limited to intestinal transporters) that may play an important role in their pharmacokinetics ( Table 2 ). When the drug is listed as a substrate in the UCSF-FDA Transportal database 28 , this reference will provide primary reference sources.

There are currently two major drug classification systems in use, the BCS and the BDDCS, which are based on the solubility and nominally the permeability of a drug. The BCS was developed to allow waiver of in vivo bioequivalence studies for highly soluble, highly permeable drugs, where rapid dissolution of immediate release dosage forms could be established 1 , 29 . However, as pointed out by Benet and Larregieu 30 , the definitive criteria for assignment of Class 1 BCS is ≥ 90% absorption, and, in fact, a number of poor permeability rate drugs relative to metoprolol (e.g., cefadroxil, cephradine, levofloxacin, loracarbef, ofloxacin, pregabalin, and sotalol) showing ≥ 90% absorption are assigned to BCS Class 1 31 . In contrast, BDDCS was developed to predict drug disposition based on solubility and permeability rate, with the recognition that high permeability rate compounds were eliminated primarily by metabolism, while poor permeability rate drugs were eliminated by renal and biliary excretion of unchanged drug 2 . A strength of the BDDCS for predicting disposition including drug absorption and flip-flop kinetics lies in the ability to easily obtain values for extent of metabolism that are definitive, reliable and generally consistent from study to study. Alternatively, we have recently shown that in vitro measurements of permeability rate predict BDDCS Class 3 and 4 poor metabolism with 85.6±13.1% accuracy, which is better than utilizing in vitro permeability measurements to predict BDDCS Class 1 and 2 extensive metabolism at 74±7% 32 . In the current report, all but three of the drugs found to display flip-flop kinetics were poorly metabolized and thus associated with Classes 3 and 4 of the BDDCS. Zidovudine is a particularly interesting example. It is classified as BDDCS Class 1 for its extensive metabolism in humans, in whom it lacks flip-flop kinetics; however, zidovudine is BDDCS Class 3 in rats in which it is poorly metabolized and displays flip-flop kinetics 16 , 22 .

One might expect that flip-flop kinetics would be observed with Class 2 drugs exhibiting poor solubility and/or extensive biliary recycling. However, neither we nor Yáñez et al. 4 were able to identify any BDDCS Class 2 compounds that exhibited flip-flop kinetics in humans except carvedilol 23 . Here, in 20 healthy subjects the carvedilol i.v. half-life was 2.4 h, while the terminal half-life was 4.3 h for a 50 mg suspension, and 7.1 h and 6.4 h for a 25mg and 50 mg capsule, respectively 23 . It appears here that dissolution of this poorly soluble drug yielded the flip-flop kinetics for the suspension, with disintegration of the capsule (or dissolution of unwetted particles) causing the further terminal half-life increase. As noted in Table 1 , an additional BDDCS Class 2 drug, meclofenamic acid, was found to exhibit flip-flop kinetics in horses 24 , 25 . As with the great majority of the drugs in Table 1 , meclofenamic acid exhibits a rapid i.v. half-life, 1.4 hr. Meclofenamic acid would not be expected to exhibit flip-flop kinetics in humans since the package insert indicates that following oral dosing in ten subjects the mean elimination half-life was 1.3 hr, ranging from 0.8 to 2.1 hr.

As we had expected more Class 2 poorly soluble drugs to exhibit flip-flop pharmacokinetics, we examined studies for the 60 Class2 drugs listed by Benet et al. 15 with the highest dose numbers where oral and iv data are available without finding additional drugs to add to our list. We recognize that this is a very small subset of potential studies to examine. In the BDDCS classification 15 , 230 Class 2 drugs are dosed orally, with each drug probably studied in 2 to 4 animal species plus humans. Thus, approximately 500 to 900 studies could be investigated outside of those identified as exhibiting flip-flop pharmacokinetics. Similarly 188 Class 3 and 4 orally dosed drugs may be found in the compilation 15 . Of these 188 drugs, we were able to identify 113 compounds where bioavailability following oral and iv dosing was reported in the Goodman and Gilman Pharmacokinetic Data compilations (7 th through 12 th editions). One of these drugs, zanamivir, exhibited slower oral absorption than elimination that was not identified as flip-flop pharmacokinetics in the publication 34 . We had previously identified zanamivir as exhibiting flip-flop pharmacokinetics following inhalation and intranasal administration, but did not identify the oral dosing data, and no oral dosage form of this drug had been approved (or submitted for approval), but we have included zanamivir in our listing in Table 1 . Following identification of zanamivir, we carefully reviewed other drugs approved for inhalation or nasal administration. It is possible that albuterol may exhibit flip-flop pharmacokinetics following oral dosing 35 , but our confidence in the report is not sufficient to list it here. We believe that the other two inhalation Class 3 and 4 drugs listed in Benet et al. 15 , ipratropium and terbutaline, do not exhibit flip-flop pharmacokinetics.

During the review process for this paper flip-flop pharmacokinetics was reported for the drug sapropentin dihydrochloride in infants and young children with phenylketonuria 26 . Sapropentin dihydrochloride is a synthetic preparation of the naturally occurring phenylalanine hydroxylase cofactor tetrahydrobiopterin (BH4). We have listed the drug as BDDCS Class 1 because it is dehydrated by the enzyme PCD/DCoH (pterin-4a-carbinolamine dehydratase/dimerization cofactor of hepatocyte nuclear factor 1α) 33 . However, the body regenerates BH4 in vivo and the major route of elimination in humans is via the bile. Thus, in fact, because of the regeneration process, sapropentin dihydrochloride might be considered to have BDDCS Class 3 characteristics. However, as noted in Table 2 transporter effects on sapropentin (or BH4) have not been identified.

The current findings describe a further benefit of employing the BDDCS early in drug development. It is proposed that Class 3 and 4 drugs are primarily susceptible to flip-flop kinetics in humans, and the data suggest that such disposition is likely to be most apparent and a more important consideration for drugs with relatively short half-lives. One would like to know whether a drug exhibits flip-flop pharmacokinetics so as to be able to define the rate limiting step in drug elimination, so as to be able to predict potential drug interactions and the potential liability for toxicity-lack of efficacy outcomes.

Given that transit through the small intestine takes only a few hours following gastric emptying 36 , the presence of a flip-flop phenomenon for immediate-release drugs would intuitively only be possible for drugs with half-lives not exceeding their gastrointestinal transit time. Additionally, classification as BDDCS Class 3 or 4 has implications for both drug-drug interactions as well as pharmacogenetics. In the former case, concomitant administration of another drug that affects the expression or function of a given transporter or enzyme may alter the pharmacokinetics of the drug of interest and potentially result in drug concentrations in either subtherapeutic or toxic ranges. In the latter situation, the natural variation of transporter expression or function also has the potential to affect a drug's disposition. For example, polymorphisms in OCT1 affect the pharmacokinetics of metformin in humans 37 . Thus, use of the BDDCS during early-stage development of novel drugs will help to identify those drugs that may encounter important transporter effects that require more directed characterization of their disposition.

Although flip-flop pharmacokinetics is a topic found in almost all pharmacokinetics textbooks and a topic of presentation in courses taught both in academia and in short courses taught to industrial scientists, there are very few drugs that inherently exhibit slower oral absorption than elimination (versus many controlled release drug products designed to achieve this phenomenon). This was found by Yáñez et al. 4 and in the review here. In fact, of the 698 orally dosed drugs examined by Benet et al. 15 , only 9 are here documented to exhibit flip-flop pharmacokinetics in humans.

In summary, this report demonstrates that poorly metabolized drugs in BDDCS Classes 3 and 4 are associated with flip-flop kinetics in cases where the drugs have relatively short half-lives. Furthermore, absorptive and efflux transporters may potentially play important roles in the disposition of BDDCS Class 3 and 4 drugs. It might be expected that poorly soluble Class 2 drugs should also exhibit flip-flop kinetics where absorption is limited by dissolution, although only one example was identified. The implications of these findings are that simple in vitro measures of solubility and permeability rate can be used with the BDDCS early in development in order to predict whether or not flip-flop pharmacokinetics might occur (although few drugs would actually be expected to do so) and gut transporters are likely to influence the in vivo pharmacokinetic behavior of a new molecular entity. Thus, BDDCS classification helps to identify compounds early on for which increased characterization of transporter interactions may be necessary for the purpose of predicting potential drug-drug interactions including transporter-enzyme interplay, as well as assessing the potential importance of pharmacogenetic variability in a population.

Acknowledgments

The work presented here was supported in part by NIH grants GM75900 and GM61390.

Abbreviations

Study of Flip Flops

Prior to the lab session:

• Study the operation and working principle of RS, JK, D and T flip-flops.
• Study the procedure for conducting the experiment in the lab.

Objectives:

To construct RS, JK, D and T flip-flops and verity their truth tables.

• IC 7476                                     -           1No.
• IC Trainer kit                              -           1No.
• Connecting patch chords           

In digital circuits, a FIip-FIop is a term referring to an electronic circuit (a bistable multivibrator) that has two stable states and thereby is capable of serving as one bit of memory. A flip-flop is usually controlled by one or two control signals and /or a gate or clock signal. The output often includes the complement as well as the normal output.

SR FIip-FIop:

The fundamental latch is the simple SR  flip-flop, where S and R stand for set and reset respectively. It can be constructed from a pair of cross-coupled NOR logic gates. The stored bit is present on the output marked Q.

Normally, in storage mode, the S and R inputs are both low, and feedback maintains the outputs in a constant state, with Q and the complement of Q. If S (Set) is given with high while R is held low, then the Q output is forced high, and stays high even after S returns low; similarly, if R (Reset) is given with high while S is held low, then the Q output is forced low, and stays low even after R returns low.

JK-FIip-FIop:

The JK flip-flop augments the behavior of the SR flip-flop (J = Set, K = Reset) by interpreting the S = R = 1 condition as a “flip“ or toggle command. Specifically, the combination J = 1, K = 0 is a command to set the flip-flop; the combination J = 0, K = 1 is a command to reset the flip-flop; and the combination J = K = 1 is a command to toggle the flip-flop, i.e., change its output to the logical complement of its current value.

D-FIip-FIop:

The Q output always  takes on the state of the D input at the moment of a rising clock edge. (or falling edge if the clock input is active low) It is called  the D flip-flop for this reason, since the output takes the value  of  the D input or Data input,  and Delays it by one clock count. The D flip-flop can be interpreted as a primitive memory cell, zero-order hold, or delay line.

T-FIip-FIop:

If the T input is high, the T flip-flop changes state (“toggles“) whenever the clock input is strobed. If the T input is low, the flip-flop holds the previous value. This behavior is described by the characteristic equation: A T flip-flop can also be built using a JK flip-flop (J & K pins are connected together and act as T) or D flip-flop.

Circuit diagrams:

JK FIip-FIop:

Truth table:

D-FIip-FIop using JK FIip-FIop:

T-FIip-FIop using JK FIip-FIop:

• Construct the RS flip flop as shown in figures 6.1 & 6.2.
• Feed the logic signals from the logic input switches observe the logic outputs on the logic Level LED indicators.
• Verify the corresponding truth tables.
• Construct JK - flip flop (fig 6.3) and repeat step 2 and 3.
• Construct D - Flip flop (fig 6.4) and repeat step 2 and 3.
• Construct T - Flip flop (fig 6.5) and repeat step 2 and 3.

Different types of Flip flops (RS, Clocked RS, JK, D, T) are Constructed using IC 7476 and hence their truth tables are verified.

Viva Questions:

• Difference between latch and flip-flop.
• List the applications of flip-flops.
• Explain the operation of JK master slave flip-flop.
• What is the difference between SR-flip flop  and clocked SR-FF.
• What is meant by level triggering and edge triggering in flip-flops.
• Explain the difference between +ve edge and -ve edge triggering.
• Which type of edge triggering is used in IC 7476 J-K MIS Flip-flop?
• Explain the preset and clear inputs of a flip-flop and why are these Called asynchronous Inputs.
• What is meant by toggle and where do  the T-FF’s are used.
• Where do the D-FF’s are used and why it is called a delay flip flop.
• Explain the race around problem in JK-FF and how it is eliminated in master slave JK- FF.

Outcomes:  

After finishing this experiment students are able to construct RS, JK, D and T flip-flops and verity their truth tables.

• Updated Jan 07, 2014
• Views 32,574

Flip-flop effect on MRI

Citation, doi, disclosures and case data.

At the time the case was submitted for publication Carlos Eduardo Barbosa Ponte had no financial relationships to ineligible companies to disclose.

Presentation

The patient, with a BMI of 15.5 (body mass index), fell on their own and fractured the right iliac bone.

Patient Data

The high signal intensity of bone marrow and subcutaneous compartments will be found on fat-suppressed fluid-sensitive sequences ( T2 fat sat and STIR) . Intermediate to low bone marrow and soft tissue signals will be seen on T1-weighted images.

Right iliac bone fracure.

Case Discussion

Patient has underlying osteoporosis with severe bone marrow atrophy, the MRI images show different signal appearance of the skeletal system and subcutaneous tissues.

The STIR sequence, designed to suppress signal from fat, also enhances the signal from tissue with long T1 and T2 relaxation times. In these cases, it will look like a T1-weighted image. The actual T1 will show a low signal on fat, bone marrow and soft tissue.

The "flip-flop" type of imaging leads at first to confusing signal on MRI, and some extra time with the patient in the magnet, so you could be sure all sequences were properly done.

These findings have been mainly described in cases of bone marrow atrophy .

Other related causes:

myelodysplastic syndrome

chronic renal failure

• 1. Mondal M & Gaba S. "Flip-Flop Phenomenon" - Magnetic Resonance Imaging Pitfall: A Case Report. J Radiol Case Rep. 2021;15(6):19-25. doi:10.3941/jrcr.v15i6.4271 - Pubmed
• 2. Böhm J. Gelatinous Transformation of the Bone Marrow: The Spectrum of Underlying Diseases. Am J Surg Pathol. 2000;24(1):56-65. doi:10.1097/00000478-200001000-00007 - Pubmed
• 3. Kung W & Chin W. MRI Findings of Serous Atrophy of Bone Marrow with Postirradiation Changes: A Case Report. Radiology Case Reports. 2024;19(4):1243-7. doi:10.1016/j.radcr.2023.12.045 - Pubmed
• 4. Kalamar V, Davies A, Wright P, Suresh P. MRI Findings Seen in Serous Atrophy of Bone Marrow. BMJ Case Rep. 2021;14(10):e243770. doi:10.1136/bcr-2021-243770 - Pubmed

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In this article, we will go through SR Flip Flop, we will start our article with the definition and construction of the flip-flip, and then we will go through its Basic Block Diagram with its working and characteristic block diagram, at last, we will conclude our article with its applications.

Table of Content

• Construction
• Basic Block Diagram
• Truth Table
• Function Table

Characteristic Equation

• Applications

What is SR Flip Flop?

It is a Flip Flop with two inputs, one is S and the other is R. S here stands for Set and R here stands for Reset. Set basically indicates set the flip flop which means output 1 and reset indicates resetting the flip flop which means output 0. Here, a clock pulse is supplied to operate this flip-flop, hence it is a clocked flip-flop.

What is Flip Flop?

Flip-Flop is a term that comes under digital electronics, and it is an electronic component that is used to store one single bit of information.

Diagrammatic Representation of Flip Flop

Since Flip Flop is a sequential circuit so its input is based upon two parameters, one is the current input and other is the output from previous state . It has two outputs, both are complement of each other. It may be in one of two stable states, either 0 or 1.

Prerequisite : Introduction of Sequential Circuits

Construction of SR Flip Flop

We can construct SR flip flop with two ways, one is with 2 NOR Gates + 2 AND Gates and other is with 4 NAND Gates .

Ways to Construct SR Flip Flop

SR Flip Flop Construction using 2 NOR + 2 AND Gates :

SR Flip Fop using two NOR and two AND Gates

SR Flip Flop Construction using 4 NAND Gates

SR Flip Flop using NAND Gate

Basic Block Diagram of SR Flip Flop

The basic block diagram contains S and R inputs, and between them is clock pulse, Q and Q’ is the complemented outputs.

SR Flip Flop basic Block diagram

Working of SR Flip Flop

• Case 1 : Let’s say, S=0 and R=0 , then output of both AND gates will be 0 and the value of Q and Q’ will be same as their previous value, i.e, Hold state.
• Case 2 : Let’s say, S=0 and R=1 , then output of both AND gates will be 1 and 0, correspondingly the value of Q will be 0 as one of input is 1 and it is a NOR gate so it will ultimately gives 0, hence Q gets 0 value, similarly Q’ will be 1.
• Case 3 : Let’s say, S=1 and R=0 , then output of both AND gates will be 0 and 1, correspondingly the value of Q’ will be 0 as one of input to NOR gate is 1, so output will be 0 ultimately and this 0 value will go as input to upper NOR gate, and hence Q will become 1.
• Case 4 : Let’s say, S=1 and R=1 , then output of both AND gates will be 1 and 1 which is invalid, as the outputs should be complement of each other.

Truth Table of SR Flip Flop

Given Below is the Truth Table of SR Flip Flop

Here, S is the Set input, R is the reset input, Qn+1 is the next state and State tells in which state it enters

Function  Table of SR Flip Flop

Given Below is the Function Table of SR Flip Flop

Here, S is the Set input, R is the reset input, Qn is the current state input and Qn+1 is the next state outputs.

• The characteristic equation tells us about what will be the next state of flip flop in terms of present state.
• In order to get the characteristic equation, K-Map is constructed which will be shown as below:

• If we solve the above K-Map then the characteristic equation will be Qn+1 = S + QnR’

Excitation Table

• Excitation Table basically tells about the excitation which is required by flip flop to go from current state to next state.  

• Here, Qn is the current state, Qn+1 is the next state outputs and S , R are the set and reset inputs respectively.

Applications of SR Flip Flop

There are numerous applications of SR Flip Flop in Digital System, which are listed below:

• Register : SR Flip Flop used to create register. Designer can create any size of register by combining SR Flip Flops.
• Counters : SR Flip Flops used in counters . Counters counts the number of events that occurs in a digital system.
• Memory : SR Flip Flops used to create memory which are used to store data, when the power is turned off.
• Synchronous System : SR Flip Flop are used in synchronous system which are used to synchronize the operation of different component.

In this article we start from the basics of flip flops, that what actually are flip flops and then we discussed about the SR Flip Flops, the two ways in which we can construct SR Flip Flops, it’s Basic Block Diagram, Working of SR Flip Flop, it’s Truth table, Characteristic table, Characteristic equation as well as  Excitation table and in the end we discussed the Applications of SR Flip Flops.

SR Flip Flop – FAQs

What are some common design considerations when working with sr flip flops.

To design SR Flip Flop we much consider factors such as setup time, hold time, clock frequency, and power consumption.

How does the clock pulse effect the operation of an SR Flip Flop?

The clock pulse will act as a control signal which will determine the inputs(S and R) which are allowed to effect the flip flop’s output. It will synchronizes as the state transition which will occur only at specific times determined by the clock signal.

What are the key differences between an SR Flip Flop constructed using NOR gates and one constructed using NAND gates?

The main Difference between these logic implementation are SR Flip Flop constructed with NOR gates will work on active-high inputs (S=0, R=0) while the other will work on active-low inputs (S=1, R=1).

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